"We don't want people tripping over them," he said.
Stocks are replenished as they run low and although sales have been brisk, there are still plenty of titles available.
There are thousands of titles in scores of categories on sale and there are CDs, DVDs, cassettes, videos and sheet music as well.
Money raised from the annual sale goes to support the rotary club's local and overseas work.
"We have supported the Westmere Walkway development, tree plantings at Springvale Park and Matipo Park," said Mr McGowan.
"Support goes to reading assistance and Duffy Books in Schools, and we support youth leadership courses and student-exchange programmes."
Profits from the annual sale also support Whanganui Womens' Refuge, clean water programmes in Pacific Islands and equipment to support overseas aid work.
The Annual Monster Book Fair will be open from 9am on Saturday and from 10am on Sunday.
